Fences distances in overpass turbo

Here is a quick example. You have to scroll to the bottom of the "data" tab to see the results.

[out:json][timeout:25][bbox:{{bbox}}];
way[barrier=fence];
out geom;
make stats length=sum(length()),section_lengths=set(length());
out;

Script is lightly modified version of the example given in https://github.com/drolbr/Overpass-API/issues/237.

(As far as I know, there is no area evaluator, I see you've asked the similar question about that)